1. Field of the Invention
The present invention relates to a molded article made of fiber-reinforced thermoplastic material and a process for producing the same.
2. Description of Related Art
In the past, molded articles made of thermoplastic resin reinforced with fibers, such as glass fibers, have been well-known. There also has been known a process for producing the molded article made of the fiber-reinforced thermoplastic resin, the process comprising the steps of: melt-kneading the thermoplastic resin with reinforcing fibers in an extruder to produce pellets of the fiber-reinforced thermoplastic resin in which the reinforcing fibers are contained in the thermoplastic resin; feeding the pellets into an injector to melt and knead the same again to produce kneaded material; and supplying the kneaded material into a mold to form the same into a predetermined form. As a process for preparing the pellets of the fiber-reinforced thermoplastic resin by way of melt-kneading the thermoplastic resin with the reinforcing fibers, there has been known a process comprising the steps of: providing an extruder having a first opening for receiving the thermoplastic resin and a second opening, which is provided in the down flow area from the first opening, for receiving the reinforcing fibers; feeding the thermoplastic resin into the extruder through the first opening to plasticize the same in a melting zone of the extruder; adding the reinforcing fibers to the thermoplastic resin, which has reached the second opening, through the second opening; kneading the plasticized thermoplastic resin and the reinforcing fibers in a portion of the extruder between the second opening and the outlet of the extruder; and pelletizing the kneaded material. However, a problem with this method is that a large device of complex structure is required to be used because the extruder has the opening for receiving the thermoplastic resin and the opening for receiving the reinforcing fibers, separately. Additionally, the aforementioned method, in which the previously produced pellets of the fiber-reinforced thermoplastic resin are again melted and kneaded in the extruder, is problematic in that the use of the kneaded material produced by the method usually results in a molded article made of the fiber-reinforced thermoplastic resin which contains fibers of extremely short length and has undesirable physical properties because kneading of the materials is carried out in the extruder and the injector, separately, twice in total.
Several methods for producing the molded article made of the fiber-reinforced thermoplastic resin without using the pellets of the fiber-reinforced thermoplastic resin also have been known. Japanese unexamined patent publication No. Hei 2-153714, for example, discloses a method comprising the steps of: providing an injector having a first opening for receiving the thermoplastic resin and a second opening, which is provided at a down flow area from the first opening, for receiving the reinforcing fibers; feeding the thermoplastic resin through the first opening into the injector to melt the same in a melting zone of the injector; feeding the reinforcing fibers into the injector through the second opening; kneading the molten thermoplastic resin and the reinforcing fibers in the injector; and supplying the kneaded material directly into the mold to form the same. Japanese unexamined patent publication No. Hei 6-8278 discloses a method comprising the steps of: providing an injector which is provided with a single opening for receiving raw materials; feeding both the reinforcing fibers and the thermoplastic resin simultaneously into the injector through the opening; kneading the materials in the injector; and supplying the kneaded materials directly into the mold to form the same. However, the molded article made of the fiber-reinforced thermoplastic resin obtained by the above method is not always satisfactory in its physical properties such as an impact strength, because the molded article merely contains reinforcing fibers having a length of 400-500 .mu.m at most.